A prosthetic device, or prosthesis, is an artificial substitute for a part of the body such as a limb. Most prosthetic devices have sockets to attach the device to the amputee's residual limb. One of the challenges of socket design is to provide proper orthopedic contouring and positioning of the prosthetic device relative to the user's body.
Socket geometry provides support surfaces necessary for weight transfer. The socket must be able to appropriately transfer body weight onto load bearing areas and provide relief space for bony or sensitive areas. The socket therefore may not perfectly correspond to the shape of the residual limb once modifications have been made to the socket to account for sensitive areas and loading requirements. Modifications to the socket geometry may be made by using an ink pencil to mark the bony prominences and sensitive areas on the residual limb. These markings may be transferred to the cast and subsequent plaster model, which may be contoured according to the markings by the prosthetist. A temporary prosthesis then may be assembled by connecting the socket with other structural members, such as a pylon for the lower portion of the leg and a foot member. A provisional alignment may be made by estimating the appropriate overall length of the prosthesis and the relative orientation of each component. Minor adjustments then may be made while the user stands or walks.
Such a method generally requires significant time as the plaster model is modified by hand, a temporary socket is formed, the temporary socket and prosthetic alignment is tested by the user, and adjustments are made to fine tune the fit of the socket and alignment of prosthetic components.